In many printer applications, including virtually all general office applications, character-by-character reproduction on plain paper is a basic requirement; availability of the last character printed for operator inspection (last character visibility or "LCV") is always highly desirable and sometimes essential. These applications include communication printers (telex and the like), word processors, and even ordinary typewriters.
Despite an undesirably high noise level, impact printers of various kinds, including column-sequential dot matrix printers, printers having individual character keys such as conventional typewriters, and unitary font impact printers, such as "golf ball" and "daisy wheel" printers, predominate. The dominance of the impact printers results from their general capability of reproduction on plain paper on the requisite character-by-character basis, ready adaptability to provision of last character visibility, and basic economy and reliability in construction and operation.
The noise problem inherent in impact printers of all kinds is effectively eliminated in electrostatic printers and in electromagnetic printers, which have been successful in some high high speed and high volume printing applications. These devices, however, have not proved competitive in general office applications requiring machines of minimal complexity and subject to only moderate requirements as regards speed or volume of output. On the one hand, electrostatic and electromagnetic printing techniques are difficult to adapt to character-by-character data reproduction, and are even more difficult to apply to a printer affording LCV capability. On the other hand, when adapted to individual character reproduction the cost and complexity of reliable electrostatic or electromagnetic printing mechanisms capable of printing on plain paper tend to be excessive as compared with impact printers.